The ability to crawl through long, flexible, and curved tubes has long been a challenge for engineers since numerous applications can benefit from a reliable solution. This ranges from medical applications for treatment and diagnosis to sewer pipes, gas pipes and power plants.
Current solutions often contain a payload such as a camera, that is pushed from the back by a long flexible rod or wire. This is the solution currently used in most medical applications with guide wires or catheters as used to deliver diagnosis or treatment instruments to the desired position, e.g. catheterization, colonoscopy, ureteroscopy, dilating balloon, and others.
In some type of applications it is impossible to push the active head from the back because the force required would cause buckling of the long rod or wire. One of the biggest shortcomings of current endoscopes and catheters is that they are pushed into the human body manually over a curved path, thereby causing friction, and possible injuries to the inner tissue walls of the lumen.
In search for a solution, a number of locomotion types of propulsion have been developed, which pull at the distal end of the lumen rather than pushing at the proximal end. Examples in non-medical applications include crawling vehicles and spider-like robots, such as are described in U.S. Pat. Nos. 6,824,510, and 5,090,259. In medical applications the most common solution is that of the inch worm type, that advances by means of peristaltic motion, such as is described, for instance, in U.S. Pat. Nos. 6,764,441, 4,176,662, 5,090,259, 5,662,587, 6,007,482 and 5,364,353, and in the article by P. Dario, et al., “Development and in vitro testing of a miniature robotic system for computer-assisted colonoscopy,” published in Computer Aided Surgery, Vol. 4, pp. 1-14, 1999, and in the article “A Locomotive Mechanism for a Robotic Colonoscope” by Byungkyu K, et al., published in Proceedings of the IEEE/RSJ Intl. Conference on Intelligent Robots and Systems; 2003, pp. 1373-8. Another type of medical application device is described in U.S. Pat. No. 6,702,735.
Another solution is one which imitates the locomotion of the earth-worm (Annelida), that generates waves of contraction and relaxation of alternate muscle groups (longitudinal and circular muscles), causing the worm to move forward, such as is described in the article by J. Dietrich et al., entitled “Development of a peristaltically actuated device for the minimal invasive surgery with a haptic sensor array” published in Micro- and Nanostructures of Biological Systems, Halle, Shaker-Verlag, 69-88. ISBN 3-8322-2655-9. Another solution suggested uses motion hydraulically generated close to the tip, such as is described in U.S. Patent Application 2005/0033343, for “Catheter Drive” to I. Chermoni.
Most of the above described devices have the disadvantage that a number of control lines or pneumatic tubes are required to operate the device, which complicates both the control system and the physical deployment of the device within the passageway. The device described in the above-mentioned U.S. Pat. No. 5,364,353 for “Apparatus for advancing an object through a body passage” to M. T. Corfitsen et al., on the other hand, requires only one inflation tube. In this patent, there is described a device using a single bladder and an axially expandable bellows with a throttle valve between them. A tube is provided with a lumen for the supply and removal of inflation medium to the bladder and bellows. The throttling valve ensures that the inflation of the bladder is delayed relative to the axial expansion of the bellows as pressure is applied to the inflation tube, and that the deflation of the bladder is delayed relative to an axial contraction of the bellows as pressure is released from the inflation tube, such that the device can be advanced stepwise through, for instance, a gastrointestinal canal.
However, the device described in U.S. Pat. No. 5,364,353 has a drawback, which may make it problematic for use in real life situations. The device moves forward by means of axial expansion of the bellows section followed by radial anchoring of the bladder section against the inside of the passageway being negotiated, and then pulling forward of the bellows section and its trailing inflation tubes while the bladder is still anchored by its inflation pressure. However, during the forward creeping stage of the bellows, the applicants state that the device uses the bends in the trailing inflation tube to provide the friction and hence the resistance against which the device is pushed forward, this backward resistance preventing the inflation tube from being pushed back, and ensuring that the device tip moves forward.
However, the very same friction in the trailing tubing used as a rear anchor for the device when moving forward, will tend to prevent the device from pulling the trailing tubes forward as the bellows deflates. In order to pull the trailing tubing forward, the front bladder of the device presumably needs to grip the internal passageway strongly, which may not be desirable in some cases. In order to overcome reliance on the rearward friction as described in U.S. Pat. No. 5,364,353, such a device should therefore have some additional mechanism that anchors the device in place during the inflation phase.
Most of the above described devices therefore appear to have various disadvantages which limit their usefulness in one aspect or another, such that there is need for a new, distally propelled catheter head which can operate simply, over long tracts of internal passages, and without causing undue damage to the inner walls of the passages.
The disclosures of each of the publications mentioned in this section and in other sections of this application, are hereby incorporated by reference, each in its entirety.